The system time of a data processing system is measured by a system clock, which is typically implemented as a simple count of the number of ticks/interrupts that have transpired since some arbitrary starting date and time. The system time may be inaccurate for several reasons. For example, the stability of the interrupt requests may drift over a period of time, thereby altering the rate of interrupts. Thus, the system time may drift and be inaccurate. However, in some data processing systems, it may be important to ensure the accuracy of the system time. For example, it may be important to maintain a certified system time to ensure that certain computer processes are performed at a precise time. In addition, because file systems keep track of the times that files are created, modified, and/or accessed by storing timestamps in the file control block of each file using the system time, an accurate system time is required to ensure the accuracy of the timestamps.